1. Related Applications
This application is related to allowed, co-pending U.S. patent application Ser. No. 07/993,332 titled ENHANCED MISSED SHIFT FROM NEUTRAL RECOVERY FOR AUTOMATED OR SEMI-AUTOMATED MECHANICAL TRANSMISSION SYSTEM and assigned to the same assignee, Eaton Corporation, as this application.
2. Field of the Invention
This invention relates to vehicular automatic or partially automatic mechanical transmission systems and, in particular, to partially automatic mechanical transmission systems of the type providing partially automatic implementation of manually or automatically selected changes or shifting of mechanical transmission gear ratios.
More particularly, the present invention relates to a control system which enhances recovery from missed shifts in a partially automatic shift implementation requiring the vehicle operator or system controller to create synchronous or substantially synchronous conditions for engagement of the transmission nonsynchronized jaw clutches.
3. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles such as heavy-duty trucks, and for automobiles, that sense throttle openings or positions, vehicle speeds, engine speeds, and the like, and automatic:ally shift the vehicle transmission in accordance therewith, are well known in the prior art. Such fully automatic change gear transmission systems include automated transmissions wherein pressurized fluid is utilized to frictionally engage one or more members to other members or to a ground to achieve a selected gear ratio as well as automated mechanical transmissions utilizing electronic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e. positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065 and 4,361,060, the disclosures of which are hereby incorporated by reference.
Such fully automatic change gear transmissions can be unacceptably expensive, particularly for the largest heavy-duty vehicles which are not typically sold in high volumes. Additionally, those automatic change gear transmissions utilizing pressurized fluid and/or torque converters tend to be relatively inefficient in terms of power dissipated between the input and output shafts thereof.
Semi-automatic transmission systems utilizing electronic control units which sense throttle position, engine, input shaft, output shaft and/or vehicle speed, and utilize automatically controlled fuel throttle devices, gear shifting devices and/or master clutch operating devices to substantially fully automatically implement operator manually selected transmission ratio changes are known in the prior art. Examples of such semi-automatic transmission systems may be seen by reference to U.S. Pat. Nos. 4,425,620; 4,631,679 and 4,648,290, the disclosures of which are incorporated herein by reference.
While such semi-automatic mechanical transmission systems are very well received as they are somewhat less expensive than fully automatic transmission systems, allow manual clutch control for low speed operation and/or do not require automatic selection of the operating gear ratio, they may be too expensive for certain applications as a relatively large number of sensors and automatically controllable actuators, such as a master clutch and/or a fuel throttle device actuator, are required to be provided, installed and maintained.
Semi-automatic shift implementation systems/methods for mechanical transmission systems for use in vehicles having a manually only controlled engine throttle means, and a manually only controlled master clutch, have been proposed. Such systems may be seen by reference to U.S. Pat. Nos. 5,053,959; 5,053,961; 5,053,962; 5,063,511; 5,050,079; 5,081,588; 5,089,962 and 5,105,357, the disclosures of which are incorporated herein by reference.
These systems may include a control/display panel or console for operator selection of upshifts, downshifts or shifts into neutral, an electronic control unit (ECU) for receiving input signals indicative of engaged gear ratio, transmission input shaft, main shaft and/or output shaft speeds and of manually selected shifts and for processing same in accordance with predetermined logic rules to issue command output signals and a transmission actuator for shifting the transmission in, accordance with the command output signals. The control/display device will typically allow the operator to select/preselect a shift into a higher ratio, a lower ratio or into neutral and will display the selected but not yet implemented shift as well as the current status of the transmission.
A concern with such automated and semi-automated systems, especially partially or semi-automatic mechanical transmission system requiring an operator to manually bring the transmission within an acceptable range of synchronous conditions (usually called the "synchronous window") before the control allows or commands engagement of a target gear ratio, is that the ranges are set at relatively small bands, to increase shift quality, which may result in the operator missing the band and becoming stuck in neutral, which is usually very undesirable.
According to the control of above-mentioned U.S. Pat. No. 5,063,511, if the selected shift is not implemented within a given period of time, the control logic will assume that the operator has missed the shift and will increase the bands or ranges to allow for a harsher shift which enhances the probability that the operator's efforts will result in implementation of the selected shift.
While the missed shift recovery system/method of above-mentioned U.S. Pat. No. 5,063,551 does considerably enhance the probability of recovering from a missed shift from neutral into a desirable target ratio, a shift into the selected desirable target ratio may remain unaccomplished.
According to the control of above-mentioned, allowed, co-pending patent application Ser. No. 07/993,332, a missed shift recovery method/system is provided which will provide an alternative for and/or a supplement to the missed shift recovery system/method of above-mentioned U.S. Pat. No. 5,063,551. According to that missed shift recovery system/method, if a shift from neutral into a desirable target ratio is not implemented within a given period of time as a result of a failure to achieve substantially synchronous conditions, the system control will determine a missed shift recovery target ratio, as a function of current engine and vehicle speed, and will then attempt to implement engagement of that ratio. The missed shift recovery target ratio (GR.sub.MSR) is selected so that the calculated engine speed at current vehicle speed and master clutch lockup (ES.sub.CALC =OS.sub.CURRENT * GR.sub.MSR) will be within the range of allowable engine speeds (ES.sub.MIN &lt;ES.sub.CALC &lt;ES.sub.MAX) and will minimize the absolute value of the expression ES.sub.CURRENT -ES.sub.CALC.
While the above-discussed two missed shift recovery strategies, separately or in combination, are effective in many situations, they are not totally satisfactory as they are based upon time in neutral, not vehicle speed or change in vehicle speed, while in neutral and attempting to complete a shift. Also, the prior art strategies require that a somewhat synchronous condition exist for engagement of a transmission gear ratio.